California passed an unusually strict equal-pay act last month, requiring that women and men within the same company be paid the same for doing “substantially similar” work, even if they have different titles, or work in different offices. The news comes on top of a recent assessment which found that California is already faring pretty well in terms of equal employment opportunities for men and women, compared to other American states.

A recent report from the Institute for Women’s Policy Research found several factors contributing to the United States’ gender pay gap. The new California law, which allows women to sue for equal pay, might help with one factor especially: the especially large gender pay gap that occurs among white-collar workers and managers.

Other women who are subject to a pay gap may not find the new law so helpful. Another major reason women as a whole are paid less than men, according to the Institute for Women’s Policy Research report: Women without college degrees are more likely to work in service jobs, such as restaurants or hospitals, while their male counterparts are more likely to work in transportation, maintenance, and other fields that pay more.